1. Field of the Invention
The present invention relates to a camera and, more particularly, to a focus area setting apparatus of a camera which sets a focus area by using information representing the direction of visual axis of the user.
2. Description of the Related Art
Conventionally, various types of information are input to a camera by means of, e.g., a dial, a button, and the like. As the amount of input information is increased, however, the operation environment is becoming complicated.
For example, a technique for detecting the direction of the visual axis of a user looking into a finder and inputting information on the visual axis to a camera is disclosed by a large number of prior arts, e.g., U.S. Pat. No. 3,804,496, Published Unexamined Japanese Patent Application Nos. 1-190177, 61-61135, 63-94232, and the like.
In some recent cameras, the focus area is arranged to cover a wide range and is automatically selected and set by the camera in order to decrease the cumbersome operation.
Even in such a camera, however, the focus area is not always automatically set at a location desired by the user. Furthermore, it is still cumbersome to set the focus area by the manual operation. Hence, it has become important to facilitate the manual setting operation required for setting the focus area at the desired location by the user.
For this purpose, an apparatus has been proposed which detects the direction of visual axis of the user looking into the finder and sets the focus area in accordance with the detection result, as described above.
When the focus area setting apparatus is used in a camera having a zoom function, although the finger performs zooming to change the magnification of the object image, the direction of the distance measurement is not changed according to the external light type distance measurement scheme. Thus, when the focus area is to be set based on only the direction of visual axis of the user, an area falling outside the distance measurement range can sometimes be selected depending on the focal length.
For example, FIG. 27 shows a state wherein the focal length is changed in an external light type in-focus detecting apparatus which can perform distance measurement in a plurality of distance measurement directions that are not changed by zooming.
In FIG. 27, on a side where the focal length of the lens is small, i.e., on the wide-angle side, the distance measurement points in the finder are as shown in FIG. 28A. The area where the focus area exists, i.e., the distance measurement enable range is the range indicated by reference symbol La.
On a side where the focal length of the lens is large, i.e., on the telephoto side, the distance measurement points in the finder are as shown in FIG. 28B. The area where the focus area exists, i.e., the distance measurement enable range is the range indicated by reference symbol Lb.
As is seen from FIGS. 28A and 28B, the distance measurement enable range in the finder changes in accordance with a change in focal length of the photographic lens, and the distance between distance measurement points in the distance measurement enable range, i.e., the resolution also largely changes. Accordingly, a correct focus area cannot be set only in accordance with the direction of visual axis of the user detected by a visual axis direction detection unit.
Also, in a so-called trimming camera which changes an apparent magnification by trimming performed during printing, if visual axis detection is performed in the same area as shown in FIG. 29 and FIGS. 30A and 30B, accurate focus area selection may not be performed.
FIG. 29 is a view showing a case wherein a trimming area is displayed by driving the liquid crystal in the finder in accordance with the trimming state.
In the trimming state shown in FIG. 29, the hatched area will not be printed. Thus, it is meaningless to set a distance measurement point 104 as a focus area.
More specifically, if uniform visual axis detection is performed regardless of the trimming state, focus areas falling outside the trimming areas of a plurality of focus areas may be erroneously selected.
FIGS. 30A and 30B are views showing cases wherein only a finder system is zoomed in accordance with the trimming state. FIG. 30A shows an ordinary finder state, and FIG. 30B shows a finder state when trimming is performed.
Problems identical to those occurring in FIGS. 28A and 28B also occur in these cases. Furthermore, in a multi-TTL AF system using non-TTL auxiliary light, when the focal length of the photographic lens is changed, the effective range of the auxiliary light is also changed. Hence, the focus area set on the basis of the direction of visual axis of the user which is detected by the visual axis detection unit sometimes falls outside the effective range of the auxiliary light. In this case, when the object has a low brightness and a low contrast, the auxiliary light is not effectively radiated, and distance measurement may not be performed.
As described above, the distance measurement enable range in the finder and the resolution of the distance measurement point are changed in accordance with a change in substantial photographic field angle due to a change in focal distance, trimming magnification, and the like of the photographic lens, and an accurate focus areas cannot be set on the basis of the direction of visual axis of the user.